Combined electromagnetic and thermal circuit breaker



April 13, 1948. w. E. snLw'ELl., JR

COMBINED. ELECTROMAGNETIC AND THERMAL CIRCUIT BREAKER Filed Dec. 5, 1942 4 Sheets-Shasta l 28 /MsuMr/cw e7 y 14. 2o 4Z k.. 5 a a, 6 2 w /w n 4mm .m W O mfym M a v l M /w 1.* 5;.. d Z 70W/ol 4 eww Jwa J m 2 W 1.46 W zwem/L 5a, f f d m i". d .4 10% I@v ..7 M h /6 2 a April 13, 1948. w. E. sTlLwELl., JR

COMBINED ELECTROMAGNETIC AND THERMAL CIRCUIT BREAKER Filed Dec. 5, 1942 Y 4 Sheets-Sheet 2 COMBINED ELECTROHAGNETIC AND THERMAL CIRCUIT BREAKER Filed Dec. 5, 1942 4 Sheets-Sheet 5 ,LMZ RNEY 0 4. 8 0 L, 0 T11 m m N Ra OW T E7 V m A l/ ,r a 5 W 4 9 m N Y. 2 L ,H 1m# m n A M N 0 April 13, 1948 w. E. s'rlLwELL, JR

COMBINED ELECTROMAGNETIC AND THERMAL CIRCUIT BREAKER Filed Dec. 5, 1942 4 Sheets-Sheet 4 INVENTOR Wma/fu, [e ORNE Mam E. 5%?

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a 3 0 7u 2 am Patented Apr. 13, 19,48

COMBINED ELECTROMAGNETIC AND THERMAL CIRCUIT BREAKER William E. Stilwell, Jr., Cincinnati, Ohio, assignor to John B. Pierce Foundation, New York, N. Y., a corporation of New York Application December 5, 1942, Serial No. 467,919

Claims. l

This invention relates to electric circuit breakers.

It is an object of the invention to provide an electric circuit breaker of small size and light weight, capable of efliciently breaking high amperage circuits at high speed, and adapted to be subjected to overload conditions without physical damage or change of calibration.

It is an object of the invention to provide a circuit breaker incorporating means for breaking the circuit under overload conditions of predetermined magnitude.

It is an object of the invention to provide a circuit breaker having ambient temperature compensation.

It is an object of the invention to provide a circuit breaker having improved operating characteristics when used as a remote control switch or as an overload protective device.

It is an object of the invention to provide a circuit breaker having improved means to minimize the effect of arcing at the load line contacts, thereby to increase the life of such contacts.

It is an object of the invention to provide a circuit breaker which will not accidentally trip under conditions of abnormal vibration or the inertia effect of sudden changes in direction, such as might be experienced in aircraft.

These and other objects and advantages will 'more fully appear from an examination of the drawings, in which Fig. 1 is a side elevation of one form of circuit breaker embodying my invention;

Fig. 2 is an enlarged elevation, in vertical central section, of the circuit breaker of Fig. 1, showing the load contacts in closed position;

Fig. 3 is a fragmentary elevation, in section, taken along lines 3-3 of Fig. 2;

Fig. 4 is a sectional plan View, taken on lines 4-4 of Fig. 3

Fig. 5 is a view similar to Fig. 2, showing the load circuit in open status;

Fig. 6 is a top plan View of the circuit breaker shown in Fig. 1;

Fig. 'I is a schematic wiring diagram for the circuit breaker of Fig. 1;

Fig. 8 is a side elevation of another embodi ment of circuit breaker embodying the invention;

Figs. 9 and 10 are elevations, in vertical central section, of the circuit breaker of Fig. 8; Fig. 9 shows the load line contacts in closed circuit position, and Fig. 10 the contacts in open circuit position;

Fig. 11 is a horizontal section through lines ll-Il of Fig. 9, showing the arrangement of an arcing disc;

Fig. l2 is a wiring diagram for the embodiment of Fig. 8;

Fig. 13 is 'an elevation of another embodiment of my invention;

Figs. 14 and 16 are sectional elevations (Fig. 16 being fragmentary) taken on lines l4|4 oi Fig. 13; in Fig. 14, the load circuit is closed, whereas in Fig. 16, the load circuit is open;

Fig. 15 is a plan section taken on lines |5-l5 of Fig. 14; and

Fig. 17 is a schematic wiring diagram for the Fig. 13 embodiment.

In the embodiment illustrated in Figs. 1 through 6, my invention comprises members 2li, 2| of aluminum or other light metallic material, inset into body members 22, 23 of electric insulation material, such as Bakelite" or equivalent. Within the hollow chamber aiorded by such combination is an aluminum ring 24 having peripheral grooves 25, 26 in parallelism. A solenoid housing 2'| iinned for heat radiation, completes the principal body structure.

Except for ring 24. the stated body members may be of mating half-portions, whereby the respective elements may be tted together and secured in any suitable manner.

In the base of solenoid housing 21 may be placed a block 28 of insulation material, to serve as a connection block for binding posts (not shown) of the control circuit.

Principal elements of the circuit breaker mechanism per se include load circuit contacts 30, 3| respectively, welded to the aluminum members 20, 2|, a snorting bar 32 adapted to bridge the gap between said contacts 30, 3|, see Fig. 2, and an arcing bridge-arm 33 having contacts 34, 35, see Fig. 4, for cooperation with fixed arcing contacts 36, 31 suitably connected into the circuit as shown in Fig. '7. The agency of connection of contacts 30, 3| into the load circuit may be the studs 38, 40 welded to housing members 20, 2|, and carrying suitable cable-receiving lugs 4|, 42.

Make and break of the 1oad-1ine contacts is accomplished by remote control through a solenoid system and therewith associated toggle spring mechanism. The solenoid system includes coils 50, 5| suitably contained and positioned within housing 21, and so associated in the electrical circuit that coil 50, the on coil, is energized when the load circuit is to be closed, and coil 5|, the oi" coil, is energized to open the load circuit, it being understood that the energization of the respective coils-'is momentary only.

Operatively associated with said coils is a magnetically responsive armature I2, suitably guided for movement under-the influence of one or the other of such coils. Said 'amature carries a shaft 53, preferably non-magneticf-to the balled Y characteristic of such toggle spring is that it hasv two positions of stable equilibrium, represented by convex or concave form, and thatthe transl-- tion from one to the other of such positions is accomplished with greatrapidity and force, and after an external iiipping"l force has been applied for less than one half of the total distance traveled by a point at the center of said toggle spring during its throw. The periphery of said toggle spring is somewhat loosely confined within the groove 25 of ring 24.

Because of the "iiipping characteristics of toggle spring 53, only a momentary energization of the solenoid coils is necessary to move the armature E2 through a sumcient distance to cause the toggle spring E@ to complete its throw under the iniiuence of its own internally generated forces.

Advantageously, engagement is made between shorting bar 32 and contacts 33. 3l, prior to the full throw of spring 56, whereby the unexpended energy of such spring acts to maintain said engagement with continuing resilient pressure.

Protection against the damaging eects of arcing at the principal load-line contacts 33, 3i is afforded by the supplemental contacts 34, 35, which respectively engage wedge-shaped fixed contacts 36, 3l, the latter being carried by an insulator 60 inset into housing member 23. Said contacts 36, 31 are electricallyconnected to the respective' aluminum housing members and thereby to the electrical circuit, by the metal plates 6I, 62 and the resistors S3. 34, respectively.

.Arcingv contact arm 33 is pivotally supported by a yoke 65 secured to insulating housing member 22, see Fig. 4. Disposed beneath said arm 33 and loosely surrounding shaft 53, which in turn passes freely through an. opening in arm 33, is

a sleeve 66 which rests upon a second double equilibrium point toggle spring Bl, supported within the circumferential groove 26 in ring 24.

Sleeve 36 abuts against the underface of arm 33,

sec Figs. 2 and 3. Y

Shaft 53 passes freely through toggle spring 61, and hence said toggle spring is not thrown by the down stroke of shaft 53.

Importantly, however, the arcing arml 33 is thrown downwardly by the impact of shorting bar 32 thereagainst, when said shorting bar is moving downwardly under the driving force of toggle spring 56 when said spring has been actuated by energization bf the o solenoid l The impact of shorting bar 32 against arm 33 after shorting bar 32 has itself attained a high velocity of movement, has two important advantages: it increases the speed of break of contacts 34, 35 with respect -to contacts 36, 3l, and it permits construction whereby said contacts 3B, 35

may be tightly wedged against the fixed contacts to improve electrical connection therebetween. Accordingly, said fixed contacts 36, 31

, maybe .of wedge formation, -thicken.' at. the topff-.

as viewed` in Fig. .4, than at the bottom. Contacts 36. 33. are secured to the ends of springable arm-portions of contact arm 33; and when arm 33 is driven upwardly under the combined efforts of toggle springs and el, acting through sleeve e8, the contacts 3.5, 3b move upwy alongcontacts 33,/ 31.*afte`rji'nitial engagement therewith,A

by the resilience of such sprlngable arm-port A wiping contact is thereby attained', Iiieeping'k therespective contacts free of oxide Vformat naand continuously come compensation are obtained by the cooperating iii-metallic elements "i3, l, disposed in the head of the circuit breaker, see Fig. 2, within a chamber formed by a suitable cap i2 of molded plastic.`

Bi-metallic element il@ is sectued` at one end to one of the aluminum housing elements, as 2o, and when relatively cool, es is the circumstance when the current through the circuit breaker is a normal load current, remains in contact with the member 23. Under over-load condition the member 23, which .provides the path of current to terminal stud 33, will experience a temperature rise and will trat the increasing temperature to the bi-metallic element to, which will warp upwardly in the direction of the contact i l. Under a sufdciently high temperature condition, the contacts lo, l! will meet, and as shown in the wiring diagram, Fig. 7, will thereupon energize the on solenoid coil and cause the circuit breaker to be thrown into open circuit position. Because of the double equilibrium point of toggle spring 53, the circuit will remain open after the bi-metallic member lo has cooled sumciently tol break contact with contact 1li and it will be necessary for the operator to close the circuit control switch ic, see Fig. 7, to re-energize the on solenoid coil to throw the circuit into closed position. f

Compensation for ambient temperature is accomplished by making contact strip li also of bimetal and attaching it to a'button i5 of aluminum or other metal having high heat conductivity which passes through the cap l2 and presents several finned radiation surfaces to the ambient temperature.

Said contact button 15 may be produced by forming said button with'an elongated cylindrical shank 'i6 which passes through a suitable aperture in the housing l2 and then is upset to form a relatively large-area stud or plate lll to` which contact strip il is attached by lrneans of the illustrated screw or equivalent.

The bi-metal of contact strip liis so arranged that when the circuit breaker is exposed to low temperatures, as may be experienced in aircraft at high altitudes, the contact strip is warped in the direction of contact strip lll,v thereby necessitating a shorter travel or extent of warping of said strip 'lil under the overload condition.

In the wiring diagram of Fig. '7, the switch 74 is schematically shown and is representative of any plurality of momentary contact switches located at any desired number of stations. The switch makes circuit through either the on contacts 16 or the off contact l1 and the respective on and oli solenoid coils are actuated during the momentary closing of the control circuit.

It will be recalled that the arc-resisting congagement with the fixed contacts 36 and 3l for a ambient temperature'.

5 moment after the main contacts 3l. 3|, 32 have been opened; and it is only when said arc-resisting contacts have been opened that -the load circuit L is in open status.

As is apparent from Fig. 7, when contact is made between the over-load and/or ambient temperature contacts 10. 1I, the ofi" solenoid coil 5|- is energized, regardless of the fact that the control 'switch 14 may be in its normal, i. e., open circuit status, and hence the load circuit L is opened automatically in the circumstance of an over-load.

In the embodiments of Figs. 8 through 11, the housing may comprise half portions |00, of equal size and shape but of opposite hand, said portions |00, |0I being of insulation material, and a metallic, preferably aluminumcoil housing |02, also of mating half portions keyed into a suitable formation in the bottom of the housing portions |00, |0| as shown in Fig. 9.

Conned within the coil housing |02, is a solenoid structure including opposed pole pieces |03, I 04, between which and a central plate are solenoid coils |06, |01, said coils being respectively the on coll and the olf coil. A magnetic armature |08 to which is secured a desirably nonmagnetic shaft |09 carries at its upper end a shorting bar l I0, which may be of silver or equivalent and which makes or breaks with the loadline contacts |I|, ||2.

The prime force driving said shaft |09 upwardly or downwardly is the toggle spring H4 which may have the previously described double equilibrium characteristic and characteristic of full throw after an impulse of less than one-half of the distance ofthe throw engendered by the respective solenoid coils |06, |01.

'The snorting bar H0 makes contact with the load contacts |I i, ||2 before the attainment of full throw position of the toggle spring I4, whereby said toggle spring maintains a positive resilient pressure on the load line contacts.

Protection against the eiIects of arcing is obtained by using a supplemental set of contacts I5, IIB in combination with a disc |1 preferably of spring silver secured to the shaft |09 immediately beneath the shorting bar ||0.

Fig. 12 shows diagrammatically the circuit connections of the respective parts of the embodiment illustrated in Figs. 8 through 11, the circuit control switch 14 functioning with respect to the therein indicated circuits similarly as the circuit control switch 14 in the circuit diagram of Fig. 1.

As indicated in Fig. 9, the spring silver disc I |1 is iiexed when the principal load line contacts are closed. Hence the silver disc ||1 remains in engagement with the contacts H5, I I6 momentarily after the load line contacts have been broken, maintaining a closed circuit status during that brief interval. The rapidity with which the hollow of the shorting bar a bi-metallic member I I8, desirably of a snap-spring formation and carrying at its center a contact button |20.

The bl-metallic snap spring I8 is influenced by the temperature of the shorting bar H0, and

as the temperature thereof rises under an overload condition, the snap spring ||8 will distort because of its bi-metailic structure until the interiorly generated forces are suicient to cause it to snap abruptly from its concave form of Fig. 9 to a convex form in which its contact |20 engages with the contact |2| disposed in the head'of the housing, as indicated in dash outline in Fig. 9.V

In the embodiment of Figs. 13 through 16, the circuit breaker housing includes a plastic cap 200 and a substantially cylindrical aluminum body portion 20| screw threadedly secured thereto as shown in Fig. 14.

Within said aluminum body portion is a coil housing 202 containing solenoid coils 203, 203a, respectively, for individual connection into the electric circuit, Fig. 17, and respectively acting upon a magnetic armature 204.

To one end of armature 204 is secured a shaft 205, carrying at its upper end a bridging contact 208 having a relatively large inturned flange 201 which functions as a contacting surface between the load line contacts 208, 2|0.

The bridging contact 206 is brought into or out of engagement with contacts 208, 2|0 by a toggle spring 2| i, said toggle spring being confined within members 2|2, 2|4. Movement of the bridging contact is initiated by the on solenoid 203 or the off solenoid 203a; said solenoids are momentarily energized and impart to the toggle spring 2|| the initial impulse effective to cause said spring to throw through its full travel.

In the base portion of housing 20|, insulated therefrom within an open-ended and open bottom insulating housing 209, is an arcing contact arm 2|5, pivotally supported as shown in Fig. 15, and carrying at one end a contact 2|5 which makes or breaks with a fixed contact 2|1. Said contacts 2| 6, 2|1 collectively form means for protecting the load line contacts 208, 2|0 from arcing, by maintaining the load circuit in closed status after the bridging contact 206 has been moved downwardly from the contacts 208, 2in under the conjoint drive of ofi solenoid 203a and toggle spring 2| l.

The arm member 2|5 is operated by means of a shaft 2|8 secured to the armature 204; a transverse bar at the end of shaft 2 8 is passed through a suitable keyhole slot in the arm 2|5 to provide a relatively7 loose connection therewith.

When the armature 204 moves upwardly to bring the shorting device 206 into engagement with the terminals 208, 2|0. shaft 2|8 rotates the arm 2| 5 about its pivot. The length of the stroke of shaft 2|8 is such that the contacts 2|6, 2|1 are engaged prior to the full stroke movement of shaft 2| 8, andthe continued movement of said shaft 2|8 fiexes arm 2|5, see Fig. 14. On the downstroke of shaft 2|8, when the circuit breaker is being activated to open-circuit position, the contacts 2|6, 2i1 remain in engagement after bridging contact 206 has moved out of engagement with the load terminals 208, 2|0, keeping the circuit closed, and preventing arcing at the principal load line contacts 208, 2|0.

Within the bridging contact 206 and in electrical connection therewith, is a bi-metallic member 220 having a contact 22| thereon, said contact being adapted for cooperation with a contact 222 secured to an end of a bi-metallic element 223, which, as shown in Fig. 16, is secured at one end to the cap 200.

The bi-metallic member 220 normally lies in surface contact with the bridging contact 206 and, in the event the temperature of said contact 200 is raised by an overload condition, the increase in temperature is transmitted by conduction to the bi-metalllc member 220. The unequal expansion of the components of the bi-metallic member 220 exes it upwardly, as appears in dotted line in Fig. 14, to a. position where its contact 22| engagesthe contact 222. Pursuant to an appropriate electrical connectin, the closing of a circuit between contacts 22| and 222 energizes solenoid coil 203a, which attracts the armature 204 downwardly and causes the toggle spring 2II to snap the bridging contact 206'out of engagement with the load line contacts 208, 2|0, whereupon the subsequently following break between contacts 2 I6 and 2I1 throws the circuit into open condition.

As is shown in Figs. 14 and 16, the cap 200 is provided with an aluminum inset 22A against a major portion of which the bi-metallic member 223 rests. The aluminum element 226 is subject to ambient temperature and transmits such temperature to the bi-metallic member 223, which moves closer to or away from the contact 22|- according to whether or not said bi-metallic element 223 is heated or cooled.

When the bi-metallic element 223 moves toward the contact 22|, as in the circumstance when the bi-metallic member 223 is cooled, the contact 22| has a lesser distance to move before striking against the contact 222, thereby affording means for compensating for variant ambient temperature and insuring that the circuit is broken only under pre-determined overload conditions.

As appears in Fig. 14, the solenoid coil housing 202, which is preferably of soft iron elements e collectively providing opposed magnetic poleengage with said xed contact'to energize the said solenoid coil and open the load circuit.

2. In an electric circuit breaker, a pair of spaced xed contacts in the circuit to be controlled, a bridging contact movable relatively thereto, solenoid means for moving said bridging contact into or out of engagement with said xed contacts, the electric circuit of said solenoid means including a switch structure having a fixed contact, and a movable contact carried by an element movable toward or away from said xed contact under the influence of temperature change in said movable element, said movable contact element being positioned in heat exchange relationship with said bridging contact to be sensible to the temperature thereof. whereupon a rise in temperature of said bridging contact beyond a predetermined value is effective to cause said solenoid circuit switch to close, to energize 'the solenoid to move the bridging contact away from the spaced lxed contacts.

3. In an electric circuit breaker having spaced, iixed contacts in the circuit to be controlled, a bridging contact to open or close th'e circuit thereacross, said bridging contact having a relatively large inturned ange, and a solenoid to vcause said bridging contact to move into open circuit position; switch means in the energizing circuit of said solenoid comprising a iixed contact and a movable contact carried by a bi-metallic member coniined within the inturned ilange of said bridging contact and in heat exchange association therewith, said bi-metallic member being so constituted that upon a rise in temperature of said bridging member the contact carried byl said bi-metallic member will close with the xed contact of said solenoid circuit to energize the solenoid to move the bridging contact out of engagement with the spaced xed contacts.

4. In an electrical circuit breaker, ilxed load contact means; movable contact means cooperatments of the invention described herein that the reciprocating elements are of light weight, and that the toggle springs have positive positions of stable equilibrium sufficient to resist inertiainduced forces tending to throw the respective magnetic armature systems in one or another direction. It has been found in actual test, that an inertia force of l5 times the acceleration 'of gravity (l5 G) is insuicient of itself to cause the circuit breaker to make or break circuit.

Whereas I have described my invention by reference to specific forms thereof, it will be understood that many changes and modifications may be made provided they do not depart from the scope of the claims.

I claim:

1. A circuit breaker comprising, in combination, switch means comprising spaced load-circuit contacts, a bridging contact for cooperation therewith in opening or closing said load-circuit, solenoid means for initiating movement of said bridging contact into open circuit position, an electro circuit for energizing said solenoid means, and a xed contact and a movable contact in said solenoid energizing circuit, said movable contact including a bi-metallic element in surface engagement with" an element of said switch means and movable toward said fixed contactl upon rise in temperature of said switch means element whereby elevated temperature engendered in said switch means element by a predetermined overload condition causes said movable contact to ing with said load circuit contact means; on and off solenoid means for controlling said movable contact means; la casing enclosing said xed load circuit contact means, said movable contact means and said solenoid means; thermostatic means disposed within said casing in heat exchange relation with said movable contact means; circuit means related to and controlled by said thermostatic means for energizing said o solenoid to disconnectsaid movable contact means with respect to said fixed load circuit contact means under predetermined temperaturesarising under overload conditions under normal temperature conditions exteriorly of the casing; and thermostatic means carried by said casing responsive to temperature exteriorly of said casing and included in Asaid oi solenoid circuit means and cooperating with said llrst-named thermostatic means, whereby the electrical circuit breaker is opened under predetermined overload condition under joint temperature conditions interiorly and exteriorly of the casing of the circuit breaker.

5. Anelectrical circuit breaker under claim 4 wherein the thermostatic means responsive to temperature exteriorly of the casing is mounted within the lcasing and arranged to approach said rst-named thermostatic means under temperature conditions exteriorly of the casing lower than normal temperature.

WILLIAM E. STILWELL, JR.

(References on following page) REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Armstrong Oct. 22, 1935' Number Number 10 Name Date Brobst Mar. 24, 1925 Jennings Mar. 11, 1930 Scott Nov. 6, 1900 Badeau May 14, 1912 Robinson Apr. 26, 1910 Gregory et al Oct, 18, 1927 Beckworth' Apr. 3, 1928 FOREIGN PATENTS Country Date Australia May 25, 1939 

